Filter cartridges comprise a filter medium that surrounds a cavity. The cavity has at least one opening into which compressed air can be blown. The filter cartridges comprise a pleated or folded filter medium that can be welded or glued at end regions to form a prismatic body.
Filter cartridges of this kind for filtering air contain, as a core part, a filter medium arranged in the shape of a star that is assembled from a flat medium. In addition to the folding or pleating and the fold orientation, a significant process step in the assembly is that of joining the end folds of a planar concertina to form a prism.
A filter cartridge can have a relatively low resistance to pressure surges if two end folds are glued together “back-to-back” and extend together in the radial direction, as shown in FIG. 1.
Although DE 10 2012 015 876 A1 and DE 101 35 421 A1 disclose ultrasonic welding methods, experiments have shown that ultrasonically welded end folds that are “back-to-back” have mechanical strength properties that do not meet the requirements and mechanical strength properties that can be achieved by gluing.
Although gluing techniques for joining overlapping end folds of concertinas are known, there is a need to be able to use overlapping of this kind in a reliable manner.
In this case, technically reliable joining of the filter medium must be achieved and ensured since, in use, said join is subjected to mechanical stresses, sometimes over several years.
In practice, very varied filter media are used, depending on the purpose of the filtration. A corresponding method for joining the end folds must therefore make it possible to reliably process different filter media having in part very different physical properties. Joining of this kind can be achieved by means of adhesive technology.